Along with the release of iTunes 11, Apple also pushed a new update to Apple TV 2nd and 3rd generation. Latest update brings iOS to version 5.1.1, which includes support for the new mode of Up Next, iTunes 11 support, iTunes Match to see which songs in the playlist below and various corrections related to the overall improvement of the stability of the OS. The upgrade is available for the Apple TV second and third generation.
Apple TV 2nd Generation (Download here)
Apple TV 3rd Generation (Download here)